Method for forming a semiconductor device structure a semiconductor layer
View Patent ↗A method for providing gates of transistors with at least two different work functions utilizes a silicidation of two different metals at different times, silicidation for one gate and polysilicon for the other, or silicidation using a single metal with two differently doped silicon structures. Thus the problem associated with performing silicidation of two different metals at the same time is avoided. If the two metals have significantly different silicidation temperatures, the one with the lower temperature silicidation will likely have significantly degraded performance as a result of having to also experience the higher temperature required to achieve silicidation with the other metal.
1. A method for forming a semiconductor device structure in a semiconductor layer, comprising:
forming a first region and a second region of opposite conductivity type in the semiconductor layer, the first region and the second region being electrically isolated by an isolation region;
forming a control electrode dielectric overlying the first region and the second region;
forming a silicon-containing layer overlying and in contact with the control electrode dielectric;
doping a first portion of the silicon-containing layer with a first predetermined dopant material;
doping a second portion of the silicon-containing layer with a second predetermined dopant material;
depositing a metal layer overlying the silicon-containing layer;
annealing the semiconductor device to form a first control electrode silicide in the first portion of the silicon-containing layer and to form a second control electrode silicide in the second portion of the silicon-containing layer;
forming a first control electrode from the first control electrode silicide and forming a second control electrode from the second control electrode silicide; and
completing formation of a first transistor using the first control electrode and completing formation of a second transistor using the second control electrode.
2. The method of claim 1 wherein the depositing of the metal layer further comprises:
selectively depositing a first metal layer overlying the first portion of the silicon-containing layer;
forming a first silicide control electrode by annealing the semiconductor device at a first temperature;
selectively depositing a second metal layer overlying the second portion of the silicon-containing layer; and
forming a second silicide control electrode by annealing the semiconductor device at a second temperature that is substantially lower than the first temperature;
wherein the first silicide control electrode has a different work function than the second silicide control electrode.
3. The method of claim 1 further comprising:
depositing the metal layer as a single metal layer overlying both the first portion and the second portion of the silicon-containing layer.
4. The method of claim 1 further comprising:
exposing the semiconductor device structure in an oxygen rich environment prior to forming the second control electrode silicide, the oxygen rich environment modifying a thickness of a portion of the control electrode dielectric that is not underlying the first control electrode silicide.
5. The method of claim 1 further comprising:
depositing in-situ doped polysilicon overlying the first control electrode silicide and the second control electrode silicide for use as part of the first control electrode and the second control electrode.